Carton filling apparatus



Oct. 27, 1959 c. E. KERR CARTON FILLING APPARATUS Original Filed Dec. 31, 1948 e Sheets-Sfieet 1 d F 4. EHIIMHI I- N 9% m 9 MM MM 7 NM x A Q F & 0 mm 0 s a, v QQO HE 5 0 0 5 @Q Q Q\\ N\ O 2 w 0% 0 Fa 7 wk 5 3w 0 N 0. s Q m w\ QM N\ 0 m3 m @\0 lv v! V MM. 3 Q I I ATTORNEY 6 Sheets-Sheet 2 QWN MWN

INVENTOR CHARLES E. KERR c. E. KERR CARTON FILLING APPARATUS Original Filed Dec. 51, 1948 v3 o A. MQ N 9 Oct. 27, 1959 5 QQ A o A QQ ATTORNEY Oct. 27, 1959 c. E. KERR r CARTON FILLING APPARATUS Original-Filed Dec. 51. 1948 6 Sheets-Sheet 3 INVENTOR CHARLES E. KER/7 av M '52. W.

, m'onuev Oct. 27, 1959 c. E. KERR ,2

CARTON FILLING APPARATUS Original Filed Dec. 31, 1948 6 Sheets-Sheet 4 INVENTOR CHARLES E. KERR.

ATTORNEY.

Oct. 27, 1959 c. E. KERR 2,910,212

CARTON FILLING APPARATUS Original Filed Dec. 31. 1948 6 Sheets-Sheet 5 FIE E INVENTOR CHARLES E. KERR BY'HWM'ZW ATTOR NEY Oct. 27, 1959 c. E. KERR A CARTON FILLING APPARATUS Original Filed Dec. 51. 1948 I 6 Sheets-Sheet 6 RR mm. K 5. v m

m M M ATTORNEY United States Patent CARTON FILLING APPARATUS Charles E. Kerr, Hoopeston, Ill., assignor to Food Machinery and Chemical Corporation, San Jose, Calif., a corporation of Delaware Original application December 31, '1948, Serial No. 68,484, now Patent No. 2,762,274, dated September 11, 1956. Divided and this application January 13, 1954, Serial No. 403,675

6 Claims. (Cl. 222168.5)

The present invention relates to carton filling apparatus.

This application is a division of my copending application Serial No. 68,484, filed December 31, 1948, which issued on September 11, 1956 as Patent No. 2,762,274, for Carton Erecting Apparatus.

An object of my invention is to provide a novel and improved carton filling apparatus especially suitablefor incorporation in and use with carton feeding, filling and sealing systems for handling cartons of the end-fill type.

Another object is to provide a novel and improved carton filling apparatus particularly adapted for handling cartons of either the glued-end or end-lock type.

Another object is to provide a novel and reliable carton filling apparatus, of the type referred to, that is-capable of continuous operation at. high speed.

Another object is to provide for carton filling apparatus, novel and improved material supply meanssin combination with novel and improved measuring means, which material supply means is constructed and operable in a mannerto insure free flow of material therefrom into said measuring means.

Other and further objects and advantages of the present invention will become apparent from. the following description and drawings in which:

Fig. 1 is a plan view of a carton feeding, filling and sealing systern employing the carton 'filling apparatus comprehended by the present invention.

Fig. 2 is a side elevation of the system and carton filling apparatus taken along the line 2-2 of Fig. 1'.

Fig. 3 is a similar elevation of the other side of the system and carton filling apparatus taken along the line 33 of Fig. 1.

Fig. 4 is a perspective flow diagram. schematically illustrating anumber of the operations performed by the system of Fig. 1.

parts broken away for clarity .be performed in timed relation one to the other, as for example, each carton must be unfolded, one end closed and sealed, the carton filled, and then the opposite end of said carton similarly closed and sealed. Generally speaking there are two types of end-fill cartons, i.e., the end-lock type and the glued-end type. Insofar as the present disclosure is concerned, and for illustrative purposes only, I have herein elected to show and describe the carton filling apparatus of the instant invention as 'incorporated in and with a carton feeding, filling and seal- Fig. 5 IS a fragmentary plan view of the carton fill- "a 2,910,212 Patented (Jet. 27, 19.59

ing system adapted and designed for hand-ling cartons of the glued-end type.

In packaging materials of various kinds, it has become essentially and vitally important to increase the speed and reliability with which continuously operating-systems of the above mentioned type operate, not only from the standpoint of decreased cost per carton handled, but also because of the need to package frozen-food asquickly as possible after. removal from bulk freezing lockers to minimize thawing before return of the filled cartons or packaged products to the freezing lockers. With the carton filling apparatus of the instant invention, substantially increased output, speed and reliability have been attained'.

Referring now to the drawings, Fig. 1 is a plan View, as a whole, of a carton'feeding, filling and sealing: system,

the principal parts of which will now be identified. The

After each carton is filled by the apparatus'14 it is transported by the same conveyor 12 to a. second adhesiveapplying mechanism 15. Finally, after application of the adhesive or glue, the remaining openend. of the" carton is closed and is discharged from the conveyor into a compression unit 16,. the time of travel through the compression: unit being adequate for the setting of the -glue.' In Fig.1, the cartons 17 may be seen: as operativel-y positioned upon the carton-unfolding and feeding mechanism 10, but they have not been shown in the conveyor pockets 1-1. Before passing from reference to Fig. 1, it is noteworthy that the carton-unfolding and feeding mechanism 10 shown therein is of the verticallydisposed type. However, I desire to have it here understood that the carton-unfolding and feeding mechanism 10 may, when desired and deemed expedient, be of the horizontally-disposed type, the present showing being merely by way of illustration.

The vertically-disposed type of carton-unfolding and feeding mechanism 10' shown in Fig. 1 delivers unfolded and open-ended cartons 17 in succession to the conveyor pockets 11, while said pockets are in a horizontal position and are disposed in transverse relation to their a path of travel. In Fig. 4 the conveyor pockets 11 and the conveyor 12' are not shown, since such figure is merely a schematically illustrated flow diagram of the instant carton feeding, filling and sealing system. However, at the lower left-hand endo'fFig. 4 the cartons 17 are shown, as they would appear upon being discharged from the carton-unfolding and feeding mechanism 10, i.e., these cartons are unfolded and open at each end and are"hori zontally disposed in transverse relation to their path of travel.

The open-ended and unfolded cartons 17 are transported by the conveyor pockets 11 to the adhesive or glue-applying mechanism =1 3,'which effects closing and sealing of one end ofeach of said cartons. After closure of one end of each carton 17, it is transported from the mechanism 13 to the carton filling apparatus 1 4 and during" such transportation said carton isturned from its previous horizontal position to a vertical position preparatory to filling by said carton filling apparatus 14-.-

The carton filling apparatus 14 includes'a series-ofmetterial measuring pockets 28' movable in a circular path in timed relation with the conveyor 12 and the cartons 17 carried. in the U-shaped pockets 11 of said conveyor. As each carton 17 in turn arrives in registered position below a previously filled material measuring pocket 28 it is arranged to engage a carton-detecting shoe 30 which,

'by reason of displacement thereof, moves a tripping pin a stationary abutment 35 to close the gate 160 preparatory to the delivery of a further measured quantity of material into the evacuated measuring pocket 28 last mentioned. in the absence of a carton 17 from registration with a material measuring pocket 28, the no-carton, no-fill mech anism is not operated, i.e., the shoe 30 is not actuated to After leaving the carton filling apparatus 14, each carton 17 is transported in succession by its conveyor pocket 11 on the conveyor 12 to the adhesive or glue-applying mechanism 15, which efiects closing and sealing of the upper open end of said carton. After closure of the upper end of each carton 17, it is pushed from the conveyor 12,

as by plungers 43 into the compression unit 16, which maintains the cartons 17 under compression until the adhesive or glue at the freshly sealed upper ends of said .cartons has had time to set. With the above understanding of the present carton feeding, filling and sealing system as a whole, specific reference will now be made to the carton filling apparatus 14 and the manner in which it performs its designated operation.

Before proceeding with the more detailed description of the carton filling apparatus 14, it should be remembered that the cartons 17 are delivered in succession with- ;out interruption or change in speed from the carton unfolding and feeding mechanism into the conveyor U- shaped pockets 11. It should be also be remembered that as the cartons 17 leave the adhesive or glue-applying unit .13 they are still in a horizontally disposed state and are also disposed in transverse relation to their path of travel.

However, immediately after leaving the unit 13, the conveyor pockets 11, together with the cartons 17 seated therein, are titlted by any suitable means, not shown, to

a vertical position and concurrently therewith the cartons 17 are deposited in succession upon a horizontal bottom support plate 139, Figs. 2, 4, 6 and 7, with their sealed lower ends in sliding contactwith said plate, and upon which thereafter said cartons slide until they reach the compression unit 16, see Fig. 4. As each conveyor pocket 11 is tilted, its carton 17 follows along a curved guide rod 142, which is positioned to prevent dislodgement or tumbling of the carton 17 from its pocket 11. The guide rod 142, Figs. 3, 4, 5 and 6, extends horizontally to form the upper side guide to hold the cartons 17 in their vertical position on the plate 139 for continued travel with the conveyor 12. A lower side guide 143, Figs. 4 and 6, ex-

tends horizontally around the carton filling apparatus 14 in the vertical plane of the guide 142, as best shown in Fig. 6. The cartons 17 disposed in vertical position by continued movement of the conveyor are transported to the carton filling apparatus 14, their movement therethrough being in timed relation therewith.

Coming now to a detailed description of the filling apparatus or mechanism 14, Figs. 4, 5, 6 and 7, after the cartons 17 enter said apparatus, they in succession engage the carton-detecting shoe 30, which is pressed outwardly .by each carton. The shoe 30 comprises two narrow arms supported on a frame 145 which has extending therefrom a member 146 secured to a link 146a pivotally mounted at 147 and 148 between the bifurcated ends of tWQ film open the gate 160 of said pocket 28. The gate 160 of each filling or material measuring pocket 28 is opened only when there is a carton in registered position below it.

149 and 150. The arm 149 is pivoted at one end-at 151 while the arm is pivoted at 152. The arm 150 comprises the lower arm of a bell-crank, the other arm 150a of which has a bifurcated end through which set screws 153 extend to engage notches in the tripping pin 32 which is vertically disposed and so slidably mounted in a bracket 155. Movement of the shoe 30 away from pocket member 11 rotates the bell-crank 15( 150a in a clockwise direction as viewed in Fig. 7 to lift the pin 32 upwardly to :bring a roller 1 56 mounted on the upper end thereof into the path of the gate-opening element 33. The gate-opening element 33 is secured to a casting 157 which is con tinuously rotated with a ring 20312 of the filling mechanism 14. Hence, as the end of element 33 is moved into engagement with the roller 156, progress of the end of the element 33 is temporarily interrupted while the pivot pin 158 thereof continues its movement with the casting 157. The hereinbefore mentioned gate 160 attached to the element 33 and its pivot pin 158 is thereby rotated in a clockwise direction, as viewed in Fig. 7, to open the bottom of a measuring pocket 28.

As shown in Fig. 7, the associated tension spring 161 extends approximately over the pivot pin 158 and exerts a force on the end of the element 33 in a direction ten-ding to rotate it in a clockwise direction while a second tension spring 162 extends substantially to the right or in front of the pivot pin 158 to apply a substantial force to the element 33, tending to rotate it in a counterclockwise direction to maintain the gate 160 in a closed position. The opening operation, however, moves the pin 158 beyond the line of action of the spring 162 to reverse the application of the force so that both springs 161 and 162 function in a direction to move the gate 160 to the against a stop 160a, Figs. 5 and 6, which may be of rubber, the axis of the spring 162 is in a position substantially intersecting the axis of the pivot pin 158 and at that time the spring 161 is largely effective in maintaining the gate in open position. It has been found that the two springs give a better and more effective action than was attained with a single spring The foregoing action will also be apparent from an inspection of the parts in the various positions as shown in Fig. 5. Each of the gates 160 remains in fully open position for a travel time adequate for discharge of material from the measuring pockets 28 into the respective cartons. Thereafter, the associated gate-closing element 34 engages the stationary abutment 35 which is in the form of a roller, Fig. 4. The element 34 is secured to the lower end of the pivot pin 158 as best shown in Fig. 6. After engagement of the abutment or roller 35, by element 34, continued movement of the pivot pin 158 (Fig. 5) rotates the gate 160 in a counter-clockwise direction to reclose the measuring pocket 28 preparatory to filling with another charge of material to be delivered into a carton.

As shown in Figs. 1, 5 and 6, the filling machine 14 has a plurality of filling or measuring pockets 28 disposed in circular array below openings in a circular plate .163. The plate 163, Fig. 6, is carried by an annular casting 164 which has an upturned flange 165, Fig. 5, on which ride rollers 166 and 167 for the support of a hopper 168 and its associated mechanism.

The rollers, preferably rubber-tired wheels 166 and 167 carried by brackets 166a and 167a extending from one end of a frame or casting 170, form two supports for the hopper assembly, while the other end of the casting 170 rests upon a spacer 172 (Fig. 6) and forms the third support therefor. The plate 163 and the casting 164,

together with their associated supporting elements, rotate beneath the hopper 168 which, it is observed, together with the casting 170 is spaced upwardly from the plate '5 163. Accordingly, there isno wear on plate 163 to shorten its life.

The hopper 168 is carriedon the casting 170, Figs. and 6, which has a recess concentric with a stub shaft 171 for reception of the spacer 172, Fig. 6. A second spacer or washer 1-73 encircles the lower end of the shaft 171, and by means of a nut 174 the stub shaft 171 and plate 163 are locked together. Secured to the shaft 171 is a sprocket 175 carrying a drive chain 176 which is trained: over a sprocket177, arranged to drive the hopper 168 through gears 178 and 178b, Pig. 6. In this manner as. the plate 163 is rotated, the sprocket 175 rotating with it drives the hopper 168 about its vertical axis to insure free. flow of material into each telescopic measuring pocket 28. The hopper and its associated mechanism cannot rotate about the axis of shaft 171 by reason of its'bifurcated ends 176a, Figs.- 5 and 6, between which extends a stationary pin 181 secured at its lower end, Fig; 6, to a bracket 131 extending from a frame member 182. An. upwardly extending arm or stirring element 183 serves to prevent formation. of aggregates or bridges in the hopper 168. The hopper 168 is carried by the casting 170- which supports the gear 178'b. The gear 178]) is secured to the side of hopper 168 and is guided for rotation by a cover plate 184 fastened as by screws 185 to the casting 170. The plate 184 also journals a shaft 179 carrying the sprocket. 177 and gear 178.

The hopper 168 and its associated mechanism, includinga downwardly extending cylindrical member 28a for each measuring pocket 28, Pi 6, is supported by a plurality of threaded studs 190 on the rotatable. casting 1.64 extending downwardly therefrom into threaded bushings 191. Each bushing has attached to the upper end thereof a sprocket 112 about which is trained a drive chain 195. The drive chain is also trained about a sprocket 194 secured to the end of shaft 195, having at the lower end thereof an adjusting handwheel 196. By rotating the adjusting wheel 196, the threaded bushings 191 are simultaneously rotated in one direction or the other to lift or lower the casting 164 the hopper 163, and the cylindrical extensions 28:: so concurrently to increase or decrease the size of each measuring pocket as desired. An upwardly extending cylinder 28b attached tothe ring 2031) overlaps in telescoping relation the extension 28a to provide for increase or decrease of the size of each pocket.

To adjust the height of the funnels 157a (Fig. 6) formed integrally with the castings 157, a set screw 197 is loosened for rotation of a threaded bushing 199 by a handwheel 198 keyed thereto at 198a. Rotation of the handwheel 198 drives the bushing 199 threadedly enmember 2150 moves upwardly or downwardly a thrust collar 201 secured to the bushing 199 as by a set screw 202 to elevate or lower a casting 2113 having circular supporting rings 283a and 2133b secured thereto. Each casting. or sub-frame 157, being secured to the ring 2031) is moved up or down with it. Hence, all of the funnels 157a below the pockets 28 are adjusted upwardly or downwardly simultaneously relative to cartons 17 located below the funnels. A plurality of guide rods 205 is telescopically guided in cylindrical openings 206 to guide casting 203 during the adjustment by means of the handwheel 18 and bushing 119, and to drive the casting 263 from the worm wheel 2136a. Since the upper casting 164 is supported from casting 263, the hopper 168 and measuring pockets 28 as a whole are raised or lowered for adjustment of the position of the funnels 157a relative to the cartons 17 without changing the size of the measuring pockets. The structural arrangements for making the foregoing adjustments are well known to those skilled in the art.

In order that the drive for the conveyor 12 of the 6 filling machine as a whole be not disturbed during the foregoing adjustments, a floating ring sprocket 210 encircles an outer driving cylinder 2030, a part of the casting 203, and rests upon a series of rollers 211 disposed therebeneath and supported on the stationary frame memher 182. The sprocket 210 is driven from the cylinder 21130 through a key 213, Figs. 6 and 7, extending into v, a keyway 214. The keyway 214 is. vertically elongated for vertical movement of cylinder 2630 relative to the key 213 which is secured to the sprocket 210. Thus, ad-

justment of the filling assembly as-awhole does notdriven by the worth. 208. secured to a drive shaft 256, Figs. 1,. 2, 3 and 6,.driven by a motor 250.

To provide for relative angular adjustment between the measuring pockets 28 and the conveyor pockets 11, the key 213,. Fig. 7, is provided with circumferentially extending slots 213a for adjustment of the key, upon loosening cap screws 215.. That is,,..the sprocket 210 and the pockets 11 of the. conveyor 12 may be adjusted relative to the cylindrical extension of member.203 to bring each. funnel 157a extending: from a measuring pocket 28 into exact alignment witha carton therebeneath. The flexibility secured by the foregoing several adjustments makes possible the use of cartons of different heights for different volumes andyet insures that each funnel 157a will be inproper alignment and adequately close to the top of the carton to insure filling without spillage of the material being fed thereto.

If desired, the cartons may be simultaneously vibrated duringthe filling thereof, as by an eccentric 217, Fig. 2', driven by a motor 218; a .rod 219 abutting against the plate 139 which, alonga substantial area adjacent the vibrator, is not secured to any supporting means such as the lower plate 139a, Figs. 6 and 7. For the lighter materials, such as powders, the vibration of the cartons is desirable to settle the contents.

With the above understanding of the filling apparatus 14, it will be seen that. material introduced into the hopper 168, such as frozen foods, powderedor flake material, and'the like, will be agitated and maintained in free flowing state by reason of the rotation of the hopper 168 about its own axis and relative to'the sta tionary stirring arm 183. Though the hopper 168 is continuously rotated relative tomember 170, the member remains stationary; Assisting the agitation-of the material within the rotating hopper 168 are the resultant forces due. to the rotation of the pan or' plate 163 therebeneath. Since the panor plate 163 is-rotating in a counter-clockwise direction, as viewed in Fig. 5, the hopper 168 will be rotated in a clockwise direction. Accordingly, that part of the hopper to the left of center, as viewed inv Fig. 5, will be moving in the same direction as the pan or plate 163, whereas the. part to the right of center will be moving in the opposite direction. The result on the material at the bottom of the hopper will be one of agitationwhere the movement of the material within the hopper will be greater on one side than on the other, the better to feed the material into each pocket 28 as it comes beneath the hopper.

It will be recalled that the member 170 is spaced upwardlyfrom the continuously rotating pan 163 to eliminate wear thereon. This spacing. can result in slight over-filling of a measuring pocket 28 during transit beneath the hopper 168. Should some of the material move from a pocket 28 onto the rotating-pan 163, it will be carried thereby, eventually striking against guide plates 163a and 163b, Fig. 1, which intersect central- 1y of the pockets 28' after reclosure of their gates 160. In this manner, any material moved onto the pan 163 will be immediately returned to an empty measuring pocket and will thereby be placed in a carton the next time such measuring pocket is opened for discharge of its contents.

The disposition of the casting 170 above the pan 163 and the provision of the rim or upturned flange 1650f the casting 164, forming a part of the pan, is particularly desirable in not only simplifying construction but also in locating the rubber or rubber-tired wheels or rollers 166 and 167 in positions remote from any possible flow of material to them from hopper 168. The geometrical three-point support also simplifies the mounting of the hopper 168 and insures maximum mounting stability of it and its associated parts.

The driving motor 250 is included in a housing with a Reeves drive 251 or other suitable speed-changing arrangement operable as by a handwheel 252. Multiple V-belts 253 extend from a drive pulley 254 to a driven pulley 255 secured to the drive shaft 256. To one end of the shaft 256 is secured the worm 208 which meshes with the worm wheel 200a which drives the filling apparatus 14, as hereinbefore described and as shown in detail in Fig. 6. The floating sprocket 210 driven by the worm wheel 200a through the rods 205 is adapted to drive the conveyor chain 12 substantially in the manner shown in Fig. 6.

While I have shown and described a preferred em bodiment of the present invention, it will be understood that various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.

Having thus described the present invention and the manner in which the same is to be used, what I claim as new and desire to protect by Letters Patent is:

1. An apparatus for filling cartons comprising a disklike rotatable member having a plurality of measuring pockets uniformly circumferentially spaced inwardly of the edge of said rotatable member, a hopper, a frame disposed in superposed relation to said rotatable member for supporting said hopper thereabove, one portion of said frame extending to the axis of rotation of said rotatable member and two spaced portions of said frame extending into positions adjacent the edge of said member, rollers carried by said frame and bearing upon the upper face of said disk-like member providing an outer support for said frame, and means on said rotatable member adjacent the axis of rotation thereof and in supporting engagement with said frame to provide an inner support for said frame.

j 2. An automatic filling device for cartons comprising a rotatably mounted circular pan-like member having measuring pockets and an upwardly extending peripheral flange, a hopper having a discharge opening at its lower end, a frame supporting said hopper with the discharge opening of the hopper in position immediately above the pockets in the pan-like member, said frame having spaced rollers resting upon said peripheral flange, 'a stub shaft on said frame at the axis of rotation of said pan-like member, a sprocket carried by said shaft, means "for securing said shaft to said pan-like member for roing a rotatably mounted circular member having measuring pockets and an upwardly extending peripheral flange, an open-bottomed hopper, a gear surrounding the base' of the hopper and secured thereto, a frame rotatably supporting said gear and hopper with the latter in position above said pockets and closely adjacent the circular member and having spaced rollers resting upon said peripheral flange, said frame having a first stub shaft journalled therein at the axis of rotation of said circular member, a second stub shaft journalled in said frame adjacent said gear for driving the gear, driving means interconnecting said stub shafts, and means for securing said first stub shaft at said axis of rotation to said circular member for driving said second stub shaft and said hopper by said interconnecting driving means upon rotation of said circular member.

4. An automatic filling device for cartons comprising a circular member having measuring pockets and an upwardly extending peripheral flange, a hopper, a ring gear secured to the base of the hopper and concentric therewith, a frame having walls rotatably supporting said gear and hopper thereon and having spaced rollers resting upon said peripheral flange for two points of support of said hopper, said frame having a first stub shaft journalled therein at the axis of rotation of said circular member and having a second stub shaft journalled therein adjacent said ring gear, a gear carried by said last-mentioned stub shaft meshing with said ring gear, driving means interconnecting said stub shafts, means for securing an end of said first stub shaft to said circular member to form a third point of support for said frame, and means for rotating said circular member to advance said pockets and to rotate said hopper.

5. An automatic filling device for cartons comprising a circular member having measuring pockets and an upwardly extending peripheral flange, a hopper, a ring gear secured to the base of the hopper and concentric therewith, a frame having walls rotatably supporting said gear and hopper thereon and having spaced rollers resting upon said peripheral flange to support said hopper at tWo points, a first stub shaft journalled in said frame at the axis of rotation of said circular member, a second stub shaft in said frame journalled adjacent said ring gear, a gear carried by said second stub shaft and meshing with said ring gear, driving means interconnecting said stub shafts, means disposed about said first stub shaft and below a portion of said frame to form a third point of support for said frame, means for rotating said circular member to advancesaid pockets and to rotate said hopper, and stationary means connected to said frame for holding said frame against movement with said circular member.

6. A carton filling apparatus comprising a rotatable disk-like member mounted for axial adjustment and having a circular series of uniformly spaced material measuring pockets formed in a marginal portion thereof, a rotatable material supply hopper mounted for adjusting movement as a unit with the disk-like member and having a discharge outlet with which said measuring pockets successively register during rotation of said disk-like member, a gear fixed to and surrounding the base of the hopper, means for rotating said disk-like member, a first stub shaft connected to said disk-like member at the axis thereof, a rotatable drive gear meshing with said hopper gear and having a stub shaft in parallel relation to said first stub shaft, and drive means interconnecting said stub shafts to rotate said hopper upon rotation of said disk-like member.

References Cited in the file of this patent U NlTED STATES PATENTS 2,222,617 Hothersall et al. Nov. 26, 1940 2,320,581 First et al. June 1, 1943 2,639,076 Kerr May 19, 1953 

